It’s January 10 in Atlanta and there are 6 inches of snow frosting the table on my deck(!). Daily life and activity have come to a standstill, schools and shops are closed, and although the State DOT brought extra crews up from South Georgia, we are warned to “stay off the roads.” I thought I’d take a look at the effects of snow on gardens and plants.
On the plus side, the fluffy white stuff benefits plants by acting as an insulating blanket that protects landscape plants from the effects of freezing and thawing during freezing winter weather. The insulating effect is due to the unique configuration of snowflakes that includes small spaces within their structure that are filled with air, resulting in low heat conductivity. As a result, the daily temperature penetration into the snow is reduced and plants are protected from really cold dips in temperature. Flower bulbs, veggie root crops and even the crowns of dormant perennials benefit from this insulating layer of snow.
Without insulation, the water in plant cells is more likely to freeze, damaging cell walls. Frost-damaged plants are easy to spot; their growth becomes limp, blackened or takes on a translucent appearance. Evergreens turn brown. Frost problems are often exaggerated where plants face the morning sun, since this causes them to defrost too quickly, rupturing their cell walls. Snow cover mitigates these problems.
Another positive effect of snow cover is to bring otherwise shy birds right up to the doorstep. We tossed some dark pumpernickel bread crusts onto the deck; now they are gone and a group of sparrows left their little tracks in the snow.
On many soils the gradual freezing and thawing improves the physical structure of the soil. Chinese researchers led by X Deng at the Chinese Agricultural University in Beijing studied The Effects of Frost Action on Soil Physical Properties of Plough Pan. Undisturbed soil cores of loamy clay were subjected to freezing and thawing in lab, and the results indicated that this action “significantly reduced the bulk density of plough pan and increased its porosity and hydraulic conductivity.” Lighter, more porous soils are easier for roots to penetrate, yielding better plant growth in the growing season.
In Atlanta usually the snow doesn’t stick around long enough to act as a blanket for very long and I haven’t owned a snow shovel for 20+ years. In fact, I can only remember one winter back in the early 90s where the top few inches of soil actually froze. So another plus is provided when the snow melts, providing added moisture that’s good for plants.
According to Taylor’s Encyclopedia of Gardening, snow is called “the poor man's fertilizer.” As it falls, a small amount of atmospheric nitrogen and sulfur are attached to the snowflakes and sleet particles. When the snow melts it releases that nitrogen into the soil. Hardy plants green up because unfrozen ground is warm enough that growing plants can absorb this nitrogen.
Snow can be both friend and foe. A heavy layer of wet snow can cause branches to bend, break or split, and plants to uproot or fall. The Tree Care Industry Association suggests shaking excess snow from the branches of large trees, shrubs and hedges, to prevent them from becoming disfigured by the weight, particularly from broad leaf evergreens. It’s only common sense to remove heavy deposits of snow from the roofs of greenhouses and cold frames to let in light and prevent the structures from bending under the weight.
Is it snowing where you live?
Photo Credits: David Laufer, NikonJim